Process for massively producing tape type flexible printed circuits

ABSTRACT

A process for massively producing tape type flexible printed circuits is provided. The steps of pressing, etching and insulating are executed on a flexible insulation tape in reel-to-reel fashion. Thereafter, the flexible insulation tape is punched to form sprocket holes and cut along the parallel lines where the sprocket holes arrange on to become several winds of narrower flexible circuit tapes. Each flexible circuit tape has tape type flexible printed circuits and sprocket holes at two sides.

FIELD OF THE INVENTION

[0001] The present invention generally relates to a process formassively producing tape type flexible printed circuits with sprocketholes, particularly to a flexible fabrication process for massivelyproducing tape type flexible printed circuits which are applied toelectrical connectors, such as electrical connections between driver anddisplay panel, and between foldable electronic components, also even asa chip carrier of semiconductor package like Chip-On-Film package ortape carrier package, wherein the tape width of the tape type flexibleprinted circuits can be selected in a very flexible manner.

BACKGROUND OF THE INVENTION

[0002] Flexible printed circuits that can be bent and twisted are widelyapplied to the electrical connection between two electronic components.A common flexible printed circuit is installed in a LCD (liquid crystaldisplay) module as an electrical connection between LCD panel and rigidprinted circuit board.

[0003] A method for manufacturing flexible printed circuits is disclosedin U.S. Pat. No. 6,210,518, but that has not mentioned how to massiveproduce flexible printed circuits, so that the manufacturing cost offlexible printed circuits cannot be decreased effectively. Besides,among advanced electronic products the flexible printed circuits ofbeyond 0.2 mm in thickness are no longer satisfied by market, so thathow to massively produce the flexible printed circuits under 0.2 mm inthickness (flexible tape type) is a point to be solved imperatively.

SUMMARY

[0004] It is a main object of the present invention to provide a processfor massively producing tape type flexible printed circuits. The metaltraces and cover layer are formed on a flexible insulation tape with bigarea in reel-to-reel fashion, and the flexible insulation tape is cutalong the parallel lines where sprocket holes arrange on to becomeseveral strips of small flexible circuit tapes with variable width, thenreeled in reels. Therefore, it is possible to massively produce tapetype flexible printed circuits with low cost and with variable width bymeans of a set of manufacturing system.

[0005] In accordance with the process for massively producing tape typeflexible printed circuits, a copper foil and a dry film are sequentiallybonded on a flexible insulation tape which is made of polyimide,polyester, polyethylene naphthalate, liquid crystal polymer, or Teflonin reel-to-reel fashion, and a first standard point is set on theflexible insulation tape. Thereafter, the copper foil is etched to formmetal traces, and sequentially cover films are attached on the flexibleinsulation tape. Then surface treating is executed. Next, the sprocketholes are formed on the flexible insulation tape by puching and theflexible insulation tape is cut along the parallel lines where thesprocket holes arrange on to become several strips of narrow flexiblecircuit tapes, then reeled in reels. Each flexible circuit tape has aplurality of flexible printed circuits between two sides of sprocketholes. It is preferable that there is an electrical test step rightafter cutting step for testing the flexible printed circuits and markingthe defectives.

DESCRIPTION OF THE DRAWINGS

[0006]FIG. 1 is a process flowchart for massively producing tape typeflexible printed circuits in accordance with the present invention.

[0007]FIG. 2 is a three-dimensional diagram showing a provided flexibleinsulation tape reeled on a reel in accordance with the process formassively producing tape type flexible printed circuits of the presentinvention.

[0008]FIG. 3a is a side view showing the flexible insulation tape in thestep of sequentially pressing a copper foil in accordance with theprocess for massively producing tape type flexible printed circuits ofthe present invention.

[0009]FIG. 3b is a side view showing the flexible insulation tape in thestep of sequentially pressing a dry film in accordance with the processfor massively producing tape type flexible printed circuits of thepresent invention.

[0010]FIG. 4 is a side view showing the flexible insulation tape in thestep of developing in accordance with the process for massivelyproducing tape type flexible printed circuits of the present invention.

[0011]FIG. 5 is a side view showing the flexible insulation tape in thestep of etching in accordance with the process for massively producingtape type flexible printed circuits of the present invention.

[0012]FIG. 6 is a side view showing the flexible insulation tape in thestep of attaching cover films on in accordance with the process formassively producing tape type flexible printed circuits of the presentinvention.

[0013]FIG. 7 is a side view showing the flexible insulation tape in thestep of surface treating in accordance with the process for massivelyproducing tape type flexible printed circuits of the present invention.

[0014]FIG. 8 is a front view showing the flexible insulation tape in thestep of punching and cutting in accordance with the process formassively producing tape type flexible printed circuits of the presentinvention.

[0015]FIG. 9 is a cross-sectional view of manufactured tape typeflexible printed circuits in accordance with the process for massivelyproducing tape type flexible printed circuits of the present invention.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0016] Referring to the drawings attached, the present invention will bedescribed by means of the embodiments below.

[0017]FIG. 1 shows a flowchart of a process for massively producing tapetype flexible printed circuits of the present invention. A flexibleinsulation tape in the flowing procedures is shown from FIG. 2 to FIG.8.

[0018] As shown in FIG. 1, the process for massively producing tape typeflexible printed circuits of the present invention comprises: step (a)of “providing a flexible insulation tape”, step (b) of “sequentiallypressing a copper foil and a dry film”, step (c) of “developing the dryfilm”, step (d) of “etching the copper foil”, step (e) of “sequentiallyattaching cover films”, step (f) of “surface treating”, step (g) of“punching to form sprocket holes and cutting the flexible insulationtape”, and step (h) of “electrically testing”.

[0019] As shown in FIG. 2 in the step (a) of “providing a flexibleinsulation tape”, a flexible insulation tape 20 that is reeled in a reel11 is prepared. The flexible insulation tape 20 is made of polyimide(PI), Polyether (that is polyethylene terephalate (PET)), polyethylenenaphthalate (PEN), liquid crystal polymer (LCP), or Teflon. In thisembodiment the flexible insulation tape 20 is a polyimide film and has athickness about 10˜75 μm, usually it is 25 μm approximately.

[0020] The step (b) of “sequentially pressing a copper foil and a dryfilm” is shown in FIG. 3a and 3 b. As shown in FIG. 3a, at first theflexible insulation tape 20 is reeled out from a reel 11 and reeled inanother reel 11. The copper foil 30 is also reeled out from a reel, thensequentially pressed on the flexible insulation tape 20 by a laminator12 between two reels 11 so that the flexible insulation tape 20 withcopper foil 30 is reeled in another reel 11. The thickness of the copperfoil 30 is about 5˜40 μm, usually it is 18 μm approximately. Thereafteras shown in FIG. 3b, the flexible insulation tape 20 with copper foil 30is reeled out from a reel 11 again and sequentially presses a dry film40 by a laminator 12. The dry film 40 is a kind of photoimagible filmsuch as positive photoresist or negative photoresist. The flexibleinsulation tape 20 with copper foil 30 and dry film 40 is reeled in areel 11 after pressing step (b). During pressing, it is better to set aplurality of first standard points 21 at the flexible insulation tape20, such as punching through holes, for positioning the flexibleinsulation tape 20 in following steps. In another embodiment, theflexible insulation tape 20 with copper foil 30 may be provided directlyfrom supplier, it is only needed to press the dry film 40 during thepressing step (b).

[0021] In the step (c) of “developing the dry film”, as shown in FIG. 4,according to the first standard points 21 the flexible insulation tape20 is reeled out to a suitable location and length, then the dry film 40is developed to form a patterned dry film 41. Due to the first standardpoints 21 for positioning, the step (c) is executed repeatedly so thatthere is a fixed interval between each developed portion and adjacentdeveloped portion on the flexible insulation tape 20 and each developedportion is one by one and neatly arranged without declination.

[0022] As shown in FIG. 5, in the step (d) of “etching the copper foil”,the flexible insulation tape 20 with patterned dry film 41 is reeled outand etched. By means of copper chloride etching liquid, the portionsuncovered by the patterned dry film 41 are etched to make the copperfoil 30 form metal traces 31 for electrical connection. Thereafter, thepatterned dry film 41 is removed by alkaline liquid for exposing themetal traces 31. Then the flexible insulation tape 20 is reeled in reel11 after backing and setting a plurality of second standard points 22.

[0023] As shown in FIG. 6, in the step (e) of “sequentially attachingcover films”, the flexible insulation tape 20 with metal traces 31 isreeled out and a plurality of cover films 50 are sequentially attachedon the flexible insulation tape 20 with determined pressure. The coverfilms 50 are made of insulation materials such as polyimide, polyester,PEN, or LCP and have a thickness about 10˜75 μm, usually it is 25 μmapproximately. The cover films 50 have hollow portions 53 and standardholes 52 in advance. During attaching the standard holes 52 of the coverfilms 50 are pointed to the second standard points 22 of flexibleinsulation tape 20, the cover films 50 are combined to become a coverlayer 51 on the flexible insulation tape 20 for protecting the metaltraces 31 and exposing connection terminals of the metal traces 31.Alternatively, the cover layer 51 also can be a solder mask formed bymask printing or mask spraying, wherein the solder mask is a liquidphotoimagible solder mask. Executing a developing step for the soldermask is necessary to form hollows portions 53 of the cover layer 51.

[0024] As shown in FIG. 7, in the step (f) of “surface treating”, thetreatments of electroplating, tin paste printing, heat resistance, andanti-rust are executed on the flexible insulation tape 20 with coverlayer 51 to make the exposed ends of metal traces 31 form anelectroplating layer 32 or protruding electrodes, etc. Theelectroplating layer 32 is formed by non-electrolysis electroplating,gold electroplating, or tin-lead electroplating method. Also theflexible insulation tape 20 is reeled in a reel 11 after completing thestep (f) of “surface treating”. Preferably, from step (b) to step (f)are repeated until enough layers of the metal traces are formed on theflexible insulation tape 20.

[0025] The step (g) of “punching to form sprocket holes and cutting theflexible insulation tape” is shown in FIG. 8. The flexible insulationtape 20 passing the step (f) of surface treating is reeled out andpunched to form a plurality of sprocket holes 61 which arrange on aplurality of parallel lines at even number. In this embodiment, theflexible insulation tape 20 is wide enough to arrange three rows of tapetype flexible printed circuits 62. The sprocket holes 61 are formed atthe two sides of each row of the tape type flexible printed circuits 62.Then, the flexible insulation tape 20 is cut along parallel lines 23parallel to where the sprocket holes 61 arrange on by cutting orpunching method, so that the flexible insulation tape 20 is divided toseveral narrow flexible circuit tapes 60 and reeled in the reels 13.Besides, each flexible circuit tape 60 has a plurality of tape typeflexible printed circuits 62 with two rows of sprocket holes 61. Afterthe flexible circuit tapes 60 are formed, it is preferable to executestep (h) of “electrically testing” for testing the flexible circuittapes 60 and marking the defective tape type flexible printed circuits62. Usually marking holes are formed on/around the defective tape typeflexible printed circuits 62 for distinction without separating orgetting rid of defectives. Finally, the known-good completed tape typeflexible printed circuits 62 and the marked defectives are reeled in thereels 13.

[0026] According to the process for massively producing tape typeflexible printed circuits mentioned above, several winds of flexiblecircuit tapes 60 with single-layer circuits can be manufacturedsimultaneously. The cross-sectional structure of tape type flexibleprinted circuits 62 is shown as FIG. 9. The process is not only toprovide a massive production of tape type flexible printed circuits 62,but also can manufacture various width of flexible circuit tapes 60having tape type flexible printed circuits (such as 35 mm, 48 mm, 70 mmfor width) by means of a same set of producing equipment only. When awider or narrower tape type flexible printed circuits 62 are going to bemanufactured, a flexible insulation tape 20 having a width about 250 mmis provided to execute the step (b) of “sequentially pressing a copperfoil and a dry film”, the step (c) of “developing the dry film”, thestep (d) of “etching the copper foil”, the step (e) of “sequentiallyattaching cover films”, and the step (f) of “surface treating”, etc.Next in the step (g) of “punching to form sprocket holes and cutting theflexible insulation tape”, the cutting paths should be changed to formthe flexible circuit tapes with appropriate width. (for example, aprovided flexible insulation tape having a thickness about 250 mm can bedivided to 3 reels for width 70 mm, 4 reels for width 48 mm or 5 reelsfor width 35 mm of flexible circuit tapes 60). Therefore, the presentinvention can massively manufacture various kinds of standard width oftape type flexible printed circuits 62 by a same set of producingequipment so as to reach the effects of massive production and elasticalmanufacture. Besides, completed flexible circuit tapes 60 are reeled inreels 13 not only to keep the packaging cost low but also to providecustomers an automatic assembly.

[0027] As shown in FIG. 9 in accordance with the process for massivelyproducing tape type flexible printed circuits 62 mentioned above,completed tape type flexible printed circuits 62 includes a flexibleinsulated layer 64 which is made of polyimide, polyester, polyethylenenaphthalate, liquid crystal polymer, or Teflon. The flexible insulatedlayer 64 has a thickness about 10˜75 μm, also a plurality of metaltraces 31 and a cover layer 51 are formed thereon (for example, adhesive63 adhering copper foil, or a copper foil is directly pressed on theflexible insulated layer 64 with non-solidifying condition). The metallayer 31 has a thickness about 5˜40 μm and the thickness of the coverlayer 51 is 10˜75 μm approximately, so the entire thickness of tape typeflexible printed circuits 62 is thinner than 0.2 mm. The metal traces 31have electroplating layers 32 or protruding electrodes at the hollowportion 53 of protective layer 51. Therefore, the tape type flexiblecircuits board 62 that can be massively produced is extremely suitablefor electrically connecting, such as connecting display panel andprinted circuit board, and widely applied to LCD display, notebookcomputer, PDA and cell telephone, etc, even being chip carrier ofsemiconductor package.

[0028] Besides, according to the process for massively producing tapetype flexible printed circuits of the present invention, the step (b) of“sequentially pressing a copper foil and a dry film”, the step (c) of“developing the dry film”, the step (d) of “etching the copper foil”,the step (e) of “sequentially attaching cover films”, and the step (f)of “surface treating” are repeatedly executed until enough layers ofmetal traces 31 are formed on the flexible insulation tape 20.Thereafter, several winds of flexible circuit tapes with multi-layercircuit structure may be manufactured after completing the step (g) of“punching to form sprocket holes and cutting the flexible insulationtape” and the step (h) of “electrically testing”.

[0029] The above description of embodiments of this invention isintended to be illustrated and not limiting. Other embodiments of thisinvention will be obvious to those skilled in the art in view of theabove disclosure.

What is claimed is:
 1. A process for massively producing tape typeflexible printed circuits comprising the steps of: (a) providing aflexible insulation tape reeled in a reel; (b) sequentially pressing acopper foil and a dry film on the flexible insulation tape and settingfirst standard points; (c) positioning the flexible insulation tape bythe first standard points and developing the dry film to form pattern;(d) etching the copper foil to form metal traces and removing the dryfilm; (e) sequentially attaching cover films on the flexible insulationtape; (f) surface treating the flexible insulation tape to make theexposed portions of metal traces form electroplating layer; and (g)punching the flexible insulation tape to form sprocket holes arranged ineven number lines, and separating the flexible insulation tape alongparallel lines parallel to the lines where the sprocket holes arrange onby cutting or punching method to form several winds of flexible circuittapes, wherein each flexible circuit tape has a plurality of tape typeflexible printed circuits and sprocket holes at two sides.
 2. Theprocess of claim 1, further comprising: repeatedly executing step (b) tostep (f) until enough layers of the metal traces are formed on theflexible insulation tape.
 3. The process of claim 1, further comprisinga step of electrically testing for testing the flexible circuit tapesand marking the defectives after the step (g) of “punching to formsprocket holes and cutting the flexible insulation tape”.
 4. The processof claim 1, wherein the flexible insulation tape is made of polyimide,polyester, polyethylene naphthalate, liquid crystal polymer, or Teflon.5. The process of claim 1, wherein the cover films are made of polyimideor Teflon.
 6. The process of claim 1, further comprising to set secondstandard points on the flexible insulation tape for positioning thecover films after the step (d) of “etching the copper foil”.
 7. Aflexible circuit tape with tape type flexible printed circuits arrangedin a plurality of rows, each tape type flexible printed circuitcomprising: a flexible insulated layer having a thickness about 10˜75μm; a plurality of metal traces formed on the flexible insulated layerand having a thickness about 5˜40 μm; and a cover layer formed on theflexible insulated layer and having a thickness 10˜75 μm approximately,the cover layer having hollow portions for exposing the connectionterminals of the metal traces; wherein a plurality of sprocket holes areformed at two side of each row of tape type flexible printed circuits.8. The flexible circuit tape of claim 7, wherein the cover layer is madeof polyimide, polyester, or photoimagible solder mask.
 9. The flexiblecircuit tape of claim 7, further comprising an electroplating layer orprotruding electrode on the exposed connection terminals of the metaltraces.
 10. A process for massively producing tape type flexible printedcircuits comprising the steps of: (a) providing a flexible insulationtape having a copper foil on the surface and reeled in a reel; (b)sequentially pressing a dry film on the flexible insulation tape; (c)developing the dry film; (d) etching the copper foil to form metaltraces and removing the dry film; (e) forming a cover layer on theflexible insulation tape; (f) surface treating the flexible insulationtape; and (g) punching the flexible insulation tape to form sprocketholes arranged in even number lines, and separating the flexibleinsulation tape along parallel lines parallel to the lines where thesprocket holes arrange on by cutting or punching method to form severalwinds of flexible circuit tapes, wherein each flexible circuit tape hasa plurality of tape type flexible printed circuits and sprocket holes attwo sides.
 11. The process of claim 10, further comprising: repeatedlyexecuting step (b) to step (f) until enough layers of the metal tracesare formed on the flexible insulation tape.
 12. The process of claim 10,further comprising a step of electrically testing for testing theflexible circuit tapes and marking the defectives after the step (g) of“punching to form sprocket holes and cutting the flexible insulationtape”
 13. The process of claim 10, wherein in the step (e) the coverlayer is formed by attaching cover films, printing solder mask, orspraying solder mask.
 14. The process of claim 10, wherein the flexibleinsulation tape is made of polyimide, polyester, polyethylenenaphthalate, liquid crystal polymer, or Teflon.
 15. The process of claim10, wherein the cover layer is made of polyimide, polyester, orphotoimagible solder mask.